junit test cases in aem

I tried to written test cases in below controller class but facing null pointer exception

public class SiteXMLCreatorController extends WCMUse implements Controller

{

PageManager pm = getPageManager();

Page parentProvided = pm.getPage(getProperties().get("sectionparent",
                String.class));

if (parentProvided != null) {int depth_selected = Integer.parseInt((String) getProperties().get("depth"));

}

I written test cases

public class SiteXMLCreatorControllerTest

{

    SiteXMLCreatorController underTest;
    
    @Mock
    Page P_MOCK;
    
    @Mock
    PageManager PAGE_MOCK;
    
    @Mock
    ValueMap properties;
    
    @Mock
    WCMUse WCMUSE_MOCK;
    
    @Mock
    ResourceResolver resourceResolver;
 
    @Before
    public void setUp() throws Exception {
        underTest=new SiteXMLCreatorController();
        //when(underTest.getPageManager()).thenReturn(PAGE_MOCK);
    } 

@Test
    public void testGetSiteMap() throws Exception
    {
        when(WCMUSE_MOCK.getPageManager()).thenReturn(PAGE_MOCK);
        when(PAGE_MOCK.getPage("sectionparent")).thenReturn(P_MOCK);
        when(PAGE_MOCK.getContainingPage("/content/geometrixx/en").getPath()).thenReturn(P_MOCK);

}

last line of code i getting error. Please let me know how resolve it.